1. The Field of the Invention
The present invention relates generally to optoelectronic communication devices. More specifically, embodiments of the present invention relates to systems and methods for optimizing the conversion of multiple analog signals utilizing one analog to digital converter as controlled by firmware and/or software associated with optoelectronic devices.
2. The Relevant Technology
Computing and networking technology have transformed our world. As the amount of information communicated over networks has increased, high speed transmission has become ever more critical. Many high speed data transmission networks rely on optical transceivers and similar devices for facilitating transmission and reception of digital data embodied in the form of optical signals over optical fibers. Optical networks are thus found in a wide variety of high speed applications in networks of all sizes.
Typically, data transmission in such networks is implemented by way of an optical transmitter (also referred to as an electro-optic transducer), such as a laser or Light Emitting Diode (LED). The electro-optic transducer emits light when current is passed there through, the intensity of the emitted light being a function of the current magnitude through the transducer. Data reception is generally implemented by way of an optical receiver (also referred to as an optoelectronic transducer), an example of which is a photodiode. The optoelectronic transducer receives light and generates a current, the magnitude of the generated current being a function of the intensity of the received light.
Various other components are also employed by the optical transceiver to aid in the control of the optical transmit and receive components, as well as the processing of various data and other signals. For example, such optical transceivers typically include an electro-optic transducer driver (e.g., referred to as a “laser driver” when used to drive a laser signal) configured to control the operation of the optical transmitter in response to various control inputs. The optical transceiver also generally includes an amplifier (e.g., often referred to as a “post-amplifier”) configured to perform various operations with respect to certain parameters of a data signal received by the optical receiver. A controller circuit (hereinafter referred to the “controller”) controls the operation of the laser driver and post amplifier.
In addition to controlling the operation of the laser driver and the post amplifier, the controller may collect and manage diagnostic data. Performance characteristics of an optical transmitter and receiver may vary in response to changes in operational conditions like temperature and voltage. For example, the threshold current and slope efficiency of a laser diode vary with temperature. To ensure the quality and integrity of data transmission, various measurement and compensation circuits may be employed by a transceiver to compensate for these changes. The transceiver controller may evaluate operating conditions, such as, but not limited to, temperature, voltage, and low frequency changes (such as receive power) from the post-amplifier and/or from the laser driver, and then adjust component settings to compensate for any changes. The operating condition parameter values, referred to collectively as “diagnostic data”, may also be evaluated by the host computer system which typically has access to the controller via a serial interface.
In evaluating operation conditions, the transceiver's controller receives analog measurements from several sensors, converts the analog signal to a digital value, performs comparison logic with the digital values and predetermined setup data, and, finally, stores the digital operating condition values and the results of the comparison logic (collectively “digital diagnostic data”) in the controller's non-volatile memory.
The conversion of the analog operating parameter values into digital values is complicated by several factors including an increasing number of diagnostic parameters to be measured and the varying sampling rate requirements of each parameter. Further, some emerging technologies, such as passive optical networks (PONs) which use a point-to-multipoint topology, may transmit signals in a burst mode which presents an additional challenge due to the transient nature of the signal to be measured.
Assigning a dedicated analog-to-digital (A/D) converter to each signal would allow for individualized sampling rates and accuracies, and thus acquisition timing and results are guaranteed. However, multiple A/D converters would significantly increase component cost which is highly undesirable given the increasingly competitive optical transceiver market segment. In addition, having multiple A/D converters would also increase the footprint of the controller, whereas the trend in the industry is to move to smaller transceiver modules.
Alternatively, to preserve chip space, each signal may be periodically sampled in a round robin fashion using a single A/D converter. In this case, each analog value may be provided to a multiplexer, which selects in a round robin fashion, one of the signals at a time for sampling by the A/D converter. This method may work when all of the signals to be measured have the same sampling rate. However, when used in applications having highly asymmetrical sampling rates, the result is that fast signals are under-sampled and slower signals are over-sampled.
Further, the implementation of one ultra-fast A/D converter is undesirable due to the high power consumption and increased electrical noise associated with ultra-fast A/D converters. Among other problems, the increased electrical noise causes the deterioration of the front ends of weak analog signals and may violate the EMI regulations governing communications equipment.
Therefore, an optical transceiver capable of scheduling efficiently several signals having asymmetric sampling rate requirements for conversion with one A/D converter would be advantageous.